The present invention relates generally to injectors, injector systems and methods of injecting fluids, and, especially, to injectors, injector systems and methods of injecting fluids into a patient (that is, into either a human or a so called lower animal).
In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic imaging procedures. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography and urography), computed tomography (CT) scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures.
A number of injector-actuated syringes and powered injectors for use in medical procedures such as angiography, computed tomography (CT), ultrasound and NMR/MRI have been developed. U.S. Pat. No. 4,006,736, for example, discloses an injector and syringe for injecting fluid into the vascular system of a human being or an animal. Typically, such injectors comprise drive members such as pistons that connect to a syringe plunger. The drive members are in operative connection with an electric motor, which is controlled to control the reciprocal motion of the drive member. For example, U.S. Pat. No. 4,677,980, the disclosure of which is incorporated herein by reference, discloses an angiographic injector and syringe wherein the drive member of the injector can be connected to, or disconnected from, the syringe plunger at any point along the travel path of the plunger via a releasable mechanism. A front-loading syringe and injector system is also disclosed in U.S. Pat. No. 5,383,858, the disclosure of which is incorporated herein by reference.
Dual-syringe injectors such as the SPECTRIS® available from Medrad, Inc. of Indianola, Pa. are commercially available (see, for example, U.S. Reissue Pat. No. 37,602). In imaging procedure, dual-syringe injectors can, for example, enable the sequential or simultaneous injection of a contrast medium and a diluent of flushing fluid such as saline. The diluent or flushing fluid can, for example, be used to control concentration of the contrast injected or to facilitate injection of a bolus of contrast medium having desirable characteristics (for example, a well defined or tight bolus). In such dual-syringe injectors, a separate drive member or piston is provided for each syringe/syringe plunger. In turn, a separate motor and associated control circuitry and logic are provided for each motor.
Currently available injectors, and particularly, dual-syringe injectors can be quite complex and expensive to manufacture. Moreover, the nature of the MR environment can substantially increase the cost of injectors designed for use therein. In that regard, for use in an MR environment, the components of an injector are preferably fabricated from materials that are non-magnetic and/or otherwise suitable or compatible for use in an MRI environment. A review of issues related to the compatibility of various equipment in an MRI environment is set forth in Keeler, E. K. et al., “Accessory Equipment Considerations with Respect to MRI Compatibility,” JMRI, 8, 1 (1998), the disclosure of which is incorporated herein by reference. See also, Lemieux, L. et al., “Recording of EEG During MRI Experiments: Patient Safety,” MRM, 38, 943 (1997); and “A Primer on Medical Device Interactions with Magnetic Resonance Imaging Systems,” U.S Food and Drug Administration—Center for Devices and Radiological Health (Feb. 7, 1997), the disclosures of which are incorporated herein by reference.
Furthermore, electric actuators such as DC brush motors, step motors, brushless DC motors or other wound coil motors and solenoids often fail in a strong magnetic field as a result of damage to internal permanent magnets. Moreover, currents induced within the field windings of such devices from electromagnetic fields can cause overheating and potential damage to the windings and any connected electronic circuitry. The MRI magnetic field can also interfere with the device created magnetic field and prevent accurate operation.
Furthermore, differences in magnetic permeability of materials within the actuator and eddy currents induced within actuator windings can affect the homogeneity or uniformity of the MRI magnetic field, generating image artifacts. Actuators that use mechanical commutation, such as DC brush motors, can also generate radio frequency energy during switching which can induce unwanted artifacts upon the acquired MRI images. Specialized shielding and specialized materials are typically required in manufacturing injectors for use in MR environments.
For the above reasons and others, it is desirable to develop improved injectors, injectors systems and methods for injecting fluids into patients, and particularly, to develop injectors that are less complex and/or less expensive to manufacture than currently available injectors.